E. Keit1, J. Peterson1, P. A. S. Johnstone2, T. J. Robinson3, and N. B. Figura4; 1Moffitt Cancer Center, Tampa, FL, 2H. Lee Moffitt Cancer Center & Research Institute, Tampa, FL, 3Yale University, New Haven, CT, 4H. Lee Moffitt Cancer Center and Research Institute, Department of Radiation Oncology, Tampa, FL
Purpose/Objective(s): To evaluate the toxicity and palliation success rate of craniospinal irradiation (CSI) delivered via intensity modulated radiotherapy (IMRT) photon-based treatment in those with symptomatic leptomeningeal disease (LMD) as proton therapy is not yet widely accessible. Materials/
Methods: : Symptomatic patients with LMD that received IMRT-based CSI from 2018-2023 were retrospectively analyzed. Progress notes were queried for acute toxicity symptoms. Imaging and cytology were reviewed for local failure (LF). The primary end point was acute grade (G) 3 toxicity. Patients with pre-existing cytopenias were not included in cytopenia toxicity analysis. Overall survival (OS) and time to LF (TTLF) were determined via the Kaplan Meier method. Welch’s T test was used to account for unequal variance. Subgroup analysis was performed for solid tumor (STM) versus hematologic malignancies (HM). Results: Thirty-six patients received CSI. The median age at CSI was 55 (range: 25-79). There were 13 primary cancer types: nine (25%) STMs and 27 (75%) HMs. The most common pre-CSI symptoms were focal weakness and ataxia (39% each). After CSI, 77% of reported neurologic symptoms had improved or resolved. Seven patients (19%) experienced eight total G3+ toxicities: G3 fatigue (n=2), G3 nausea (n=2), G3 anemia (n=2), G3 myelitis (n=1), and G4 neutropenic fever (n=1). The median follow up was 6.5 mo (range: 0.1 – 76.3 mo). There were nine LFs; median TTLF was 7.2 mo and 4.9 mo for STM and HM, respectively. Median OS was 2.9 mo and 7.5 mo for STM and HM, respectively. One patient with STM LMD survived 67 months post-CSI. For STM, intrathecal chemotherapy (n=4, 44%) was not associated with improved OS (P=0.3).
Conclusion: As patients continue to live longer with disseminated disease, LMD will become a more commonly encountered site of spread requiring a means of palliation. Until proton therapy becomes widely accessible, IMRT-based photon therapy is an option for palliation in patients with LMD as 77% of patients experienced symptom improvement or resolution. As with all palliative radiotherapy, we caution proper patient selection as G3+ toxicity occurred in 19% of the cohort which may delay systemic therapy.
